The economy can’t catch a break: Just as unemployment looks a bit better, inflation appears. Is the Misery Index making a comeback?

That is, are we headed for a grim period like the 1970s, when Americans were slammed by both economic ills at once?

While “one swallow does not make a summer,” inflation — until now, the one good economic variable during this crisis — seems to be on the rise.

Yesterday saw the release of preliminary data on inflation in February: The consumer price index was up 0.5 percent, above expectations and the 0.4 percent jump in both January and December.

Inflation has been tame for so long — an average of just 2.5 percent a year since 1992 — that it is hard to recall a time when it was otherwise. But if you do remember, you may also recall the Misery Index.

Created in the 1960s by economist Arthur Okun, the Misery Index is a simple sum of the unemployment rate plus the inflation rate. It’s an especially potent measure because, under the Keynesian economic theories on which liberals rely, its two variables are supposed to be mutually exclusive: You get inflation or unemployment — not both.

Keynesians assume that, if unemployment gets too high, inflating the currency can stimulate the economy to reduce it. Similarly, cutting inflation must come at the price of more unemployment as the economy cools.

But those rules stopped working after 1969, as America started losing ground on both fronts at once. We even grew familiar with a new term for the plague that Keynesian theorists couldn’t explain: Accelerating inflation and increasing unemployment combined for “stagflation.”

Suddenly, both economic ills hit at once — grinding the middle class like millstones. On one side, unemployment meant a loss of income. On the other, inflation eroded savings and income.

Led by inflation in 1970, the Misery Index rose to double digits (10.6) for the first time since 1948. Over the next 15 years, it would be in single digits only once (1972), reaching its postwar high of 20.6 in 1980, when annual inflation hit 13.5 percent and unemployment 7.1 percent.

From 1970 to 1985, the Misery Index averaged 13.9.

It took the rejection of Keynesian economics by Federal Reserve Board Chairman Paul Volcker and President Ronald Reagan to slay the inflation dragon and return America to its prestagflation levels. From 1986 through 2010, the Misery Index has averaged 8.7 percent and hasn’t breached double digits since it hit 10.5 in 1992.

So the unemployment rate alone has sufficed to describe our recent economic misery — so far.

But last year, driven by a 9.6 percent unemployment rate, the Misery Index again hit double digits — 11.2, its highest level since 1984. Should unemployment stay at its February rate of 8.9 percent and inflation equal its 2.5 percent average since 1992, America would quietly have hit its highest three-year Misery Index total in two decades.

But 2.5 percent inflation is starting to look optimistic: Over the last three months, we’ve seen markedly higher rates — ones that work out to more than 5 percent at an annual rate. If that holds, we’d find ourselves firmly in line with the stagflation era’s Misery Index average.

The political impact would be huge. Jimmy Carter used the Misery Index to devastating effect in defeating President Gerald Ford, whose WIN buttons decidedly did not Whip Inflation Now. But, when Carter stuck by Keynesianism as president, Reagan in turn ousted him — in no small part thanks to the simple question: “Are you better off now than you were four years ago?”

We’ve been accustomed to negligible inflation for a generation. But if America returns to a stagflation era, we’re in for a prolonged period of economic and political upheaval.

J.T. Young served in the Treasury De partment and the Office of Management and Budget from 2001-04 and as a congres sional staff member from 1987-2000.